The final top 51 report from the NFLPA shows the Chargers with $9.393M in cap space.

That doesn't include Geathers or Addae, which now count for $0.810M.
Additionally, the $0.816M to maintain the 8-player practice squad comes out of that cap space.
Over the Cap's numbers indicate that the Chargers have $3.125M on IR and $1.909M on PUP - both of those figures now count.

So, going by these figures, the Chargers enter the season with $2.733M in cap space. At least two players will impact that exact number. If/when Ingram comes back will change his figure. Players on reserve appearently earn a reduced portion of their base salary. Additionally, Freeney's per-game roster bonuses count as a LTBE incentive. If he plays more than 14 games (what he played in 2012), he costs more. But, that figure should be a pretty good estimate for what they have available to spend on emergency moves and contract extensions.

Speaking of extensions, it is possible that the team will not come to an agreement with Donald Butler.

Sources familiar with the situation said Monday that talks are quiet between the Chargers and Eugene Parker, Butler's agent, and barring a development over the next week, negotiations will be tabled until after the season.

I do think that they will hammer out a contract extension for someone this season. However, if not Butler, I think that Rinehart is the next most likely candidate. The team could choose to retain Butler on the franchise tag next offseason, and the emergence of Geathers could be a cheaper alternative to retaining Cam Thomas - though I'd personally rather see both stick around. On the other hand, this team is already going to be looking for a starting guard in the offseason. Neither tackle is a sure thing, and center could quietly become a big need next offseason. I'd like to believe that Hardwick simply had a down year in 2012, but he's entering his 10th season, and I think we need to entertain the possibility that he's declining. He could be a cap casualty in the offseason, and leaving the Chargers looking for another starting OL... not to mention that depth is still needed across the OL. If Rinehart proves to be a solid starter, I think they make it a priority to lock him up.

However, if Butler is retained on the franchise tag...

Liuget and Butler are both in contract years in 2014.
New starters Wright, Gilchrist, and Brown are also free agents after 2014..
..as are Dunlap and Mathews

At this point, I'd expect to see the remaining A.J. Smith free agent signings get cut. Overall, they have growing base salaries and smaller amounts of dead money. The team is looking tight against the cap in the future - not bleak like some teams - and we're likely to see some cap casualties in the near future. I think Jarret Johnson has the best shot at sticking around for now, but he's the only one I think is likely to be on the team in 2014.